The PROTAC degrader of SMARCA2/4 AU-15330 effectively abolished structures of cis-regulatory elements bound by CHD6 and suppressed the growth of FH-mutated, but not FH-intact, RCC in vivo. Collectively, these data indicate that CHD6 is a molecular bridge between FH deficiency and pro-inflammatory enhancers assembly that endows FH-deficient tumors with epigenetic vulnerabilities.

We further highlight the optimization of the pharmacokinetic profile of a subset of compounds leading to potent and selective degradation of SMARCA2 in the xenograft model. These compounds provide valuable tools with desirable properties for continued exploration of the biology defining the susceptibility of SMARCA4 mutant cancers to selective loss of SMARCA2.

P2, N=60, Not yet recruiting, Prelude Therapeutics

Finally, we show that YD23 has potent tumor growth inhibitory activity in SMARCA4-mutant xenografts. These findings provide the mechanistic basis for development of SMARCA2 degraders as synthetic lethal therapeutics against SMARCA4-mutant lung cancers.

P1, N=104, Recruiting, Prelude Therapeutics | Not yet recruiting --> Recruiting

P1, N=104, Not yet recruiting, Prelude Therapeutics

Subsequent xenograft model study reveals that selective SMARCA2/4 degradation in lung tumors triggers DNA damage and apoptosis, which significantly inhibits lung cancer cell proliferation without obvious adverse events towards normal tissues. This study exemplifies the targeted degradation of SMARCA2/4 in lung cancer cells by the GSH-responsive PROTAC precursor, highlighting its potential as an encouraging cancer therapeutic strategy.

P1, N=186, Recruiting, Prelude Therapeutics | N=118 --> 186

P1, N=118, Recruiting, Prelude Therapeutics | N=86 --> 118

Secondary endpoints include objective response rate, progression-free survival, duration of response, disease control rate, and PK and PD profiles of PRT3789. The study began enrolling patients in January 2023.

The proteolysis targeting chimera (PROTAC) AU-15330 that simultaneously targets SMARCA4, SMARCA2, and PBRM1 for degradation exhibits cytotoxicity in H3.3K27M but not H3 wild-type cells...Moreover, genetic or pharmacologic targeting of FOXO1 resulted in cell death in H3K27M cells. Overall, our results suggest that H3K27M up-regulates SMARCA4 levels and combined targeting of SWI/SNF ATPases in H3.3K27M can serve as a potent therapeutic strategy for these deadly childhood brain tumors.

Our study found that the mechanisms of resistance of PROTAC degraders can vary and may be dependent on drug concentrations. Such concepts may inform future clinical decision-making regarding drug dosing.

In a CDX model of NSCLC, SCR-9140 effectively inhibits tumor growth and TGI correlates well with SMARCA2 degradation in tumors. In conclusion, our potent and selective SMARCA2 degrader, SCR-9140 induces strong synthetic lethality in SMARCA4 deficient cells in vitro and in vivo and shows great safety margin in normal cells.

P1, N=86, Recruiting, Prelude Therapeutics | Not yet recruiting --> Recruiting

P1, N=86, Not yet recruiting, Prelude Therapeutics

In subcutaneous cell-line derived xenograft (CDX) models of NSCLC, administration of PRT3789 demonstrated significant dose-related inhibition of SMARCA4-deleted NSCLC growth at tolerated doses, but no effect on the growth of SMARCA4 WT cancers. In summary, consistent with our previous validation studies and genomic perturbation analyses, our potent and selective SMARCA2 targeted degrader PRT3789 induces strong synthetic lethality in SMARCA4-deleted cancers in vitro and in vivo.

In a broader lung cancer cell line viability screen conducted with PRT1419, we observed that the presence of multiple, co-occurring alterations in SWI/SNF family members such as SMARCA4, ARID1A/B mutations and loss of SMARCA2 protein were associated with sensitivity to PRT1419. Based on these findings, preclinical evaluation of PRT1419 in other tumor types with recurrent SWI/SNF mutations is ongoing.